In various industries there are numerous parts having internal cavities which must not leak if they are to perform the function required of them, where the exact definition of not "leaking" depends on the practice in any given field.
There already exist numerous methods of leak testing a cavity, i.e. methods which serve to determine whether a cavity is in communication or not in communication with the surrounding medium via leakage paths or the like. The present Applicant has already developed a method of performing such tests and filed a (French) patent applicaiton on Sept. 10, 1984 under the No. 84 13827. This method gives very good results when the part under test is indeed leaky or not leaky.
However, some parts may be determined as being leaky when, in fact, they are not leaky. This applies to parts which include secondary, "parasitic" cavities close to their normal main cavities and connected thereto via seepage paths having very high head loss. In prior leak testing methods, and in particular in the method mentioned above, the main cavity is tested for leaks by injecting a fluid under pressure into the cavity, and then by observing pressure variation, in particular inside the cavity, it is possible to determine whether the cavity is leaky or not. However, if the cavity is connected to a secondary cavity via a seepage path having very high head loss, the quantity of fluid which may flow from the main cavity to the secondary cavity may be interpreted, when performing measurements in accordance with prior methods, as constituting a leak, even though said main cavity taken in conjunction with the secondary cavity is not leaky.
Naturally, this lack of precision can be resolved merely by waiting long enough for the test gas pressure in the cavities to come to equilibrium. Once equilibrium has been reached, the part can be leak-tested by performing measurements in accordance with a prior method.
This procedure naturally gives the desired result. However, it undeniably suffers from the drawback of considerably lengthening the time required for testing, and thus increasing the overall cost of parts tested in this way.
The object of the present invention is to mitigate the above-mentioned drawbacks, by implementing a method capable of discriminating between a leaky part and a non-leaky part having the above-mentioned characteristics, and further, capable of achieving this result in a relatively short period of time while retaining the advantages of prior leak testing methods which, in general, give very good results, very quickly.